Photoflash lamp



Oct. 3, 1961 w c F|NK PHOTOFLASH LAMP Filed D90. 31, 1959 INVENTOR WILL/AM C. F//\( ATTOR EY 3,002,367 PHOTOFLASH LAMP William C. Fink, Williamsport, Pa., assignor to Sylvania Electric Products Inc., a corporation of Delaware Filed Dec. 31, 1959, Ser. No. 863,250

2 Claims. (CI. 6731) This invention relates to photoflash lamps and more particularly to photoflash lamps characterized by a duration of light emission at useful light levels many, many times longer than that of the more popular types of presently available commercial flash lamps.

Generally speaking, the present art of making photoflash lamps is concerned primarily with photographic flash lamps which have a high intensity light peak or a certain level of light intensity for a maximum duration of about 60 milliseconds. Such a light source usually comprises an hermetically sealed envelope, provided with a protective coating and filled with a combustion-supporting gas and a combustible, usually in the form of shredded foil, which upon ignition, burns with a brilliant, fast flash. The ignition system usually comprises a pair of lead-in wires, a coating of ignition paste on the inner ends of the lead-in wires, and a fine tungsten filament attached to and supported by the lead-in wires near the inner ends thereof.

Although this type of photographic flash lamp has proved to be quite satisfactory for the more conventional usm, it has been found that, for certain applications, such as motion picture, and especially high speed motion picture, photography for example, a light source of useful light levels characterized by a duration of light emission of several seconds is highly desirable. In view thereof, the principal object of this invention is to provide such a flash lamp.

A feature of this invention is the structure employed to support the combustible.

The photoflash lamp of this invention is an improvement over the photoflash lamp shown and described in the copending application of W. C. Fink et al., Serial Number 801,807, filed March 25, 1959, entitled Photoflash Lamp, and assigned to the same assignee as this invention. In accordance with the teachings of that application, a strip of magnesium foil is supported within the lamp envelope by a wire framework, portions of which are provided with sleeves of glass tubing to protect it from the heat generated in the envelope during combustion. That suggested supporting structure represented an improvement over the supporting structure for a long-duration fiashlamp shown and described in the copending application of W. C. Fink et al., Serial Number 672,157, filed July 16, 1957, now Patent No. 2,955,447, entitled Photoflash Lamp, and assigned to the same assignee as this invention.

In accordance with the principles of this invention, a further improvement in supporting structure for the combustible is provided. In accordance with the principles of this invention, the supporting cross Wires, threaded through the corrugated foil which comprises the combustible, are shaped to conform substantially to the contour of the corrugations of the foil. 'It has been found that with this arrangement, the supporting cross wires maintain their shape and do not burn up during flashing of the lamp. It has also been found that the corrugated foil which comprises the combustible maintains its shape until consumed. These are important features because they permit flashing of the lamp in any position.

Heretofore, it had been recommended that these lamps be flashed in a vertical position with the base down as a safety precaution because of the tendency of the sup- States Patent 3,002,367 Patented Oct. 3, 1961 porting wires to burn up and the foil to collapse. When the burning foil collapses, it tends to fall toward or even into engagement with the envelope wall, sometimes melting a hole in the envelope and igniting the exterior protective coating of cellulose acetate with which the outer wall of the envelope is provided. The premature failure of the supporting structure and the collapse of the foil both contribute to a shortening of the flash duration and a substantial decrease in the total light output.

In the accompanying drawing illustrating a specific embodiment of this invention,

FIGURE 1 is an elevational view of a photoflash lamp partly broken away.

FIGURE 2 is a fragmentary detail on an enlarged scale of the strip of foil and its supporting structure.

FIGURE 3 is a top View of the strip of foil showing its corrugated configuration and the disposition of the cross supports associated therewith.

Referring now to the embodiment illustrated in the drawing, particularly FIGURE 1, the photoflash lamp comprises a sealed transparent envelope 2 of glass or the like within which a stem -4 is disposed. A pair of leadin wires 6 are supported by and extend through the stem '4, the outer ends thereof being connected to the base 10 at 12 and 14 respectively, to provide the means through which electrical energy may be supplied to a lamp filament 16 which is attached to and supported by the leadin wires at the inner ends thereof. The inner end of each of the lead-in wires 6 is provided with a gob of ignition paste 18 which usually contains an oxidizer, zirconium metal powder and nitrocellulose binder.

A strip of corrugated magnesium foil 20, preferably provided with a plurality of apertures 21 therein to aid in combustion, is supported within the envelope 2 by a framework 22. To facilitate ignition of the strip of foil 20, the lower end thereof is preferably provided with a coating 23 comprising a mixture of zirconium metal powder and nitrocellulose binder. The framework 22 comprises a substantially U-shaped nickel wire 24 and a pair of spaced, substantially parallel molybdenum wires 26 attached to the wire 24 substantially transversely thereof. A length of nickel wire 28 is attached to the bight 30 of the wire 24 substantially transversely thereof. The inner wall of the top of the envelope 2 is provided with a body of a suitable cement mixture 32 within which the cross, formed by wire 28 and bight 30, is embedded, thereby providing the means for supporting the framework 22.

The combustion supporting gas within the sealed, lighttransmitting envelope 2 is preferably the mixture described in the copending application Serial Number 672,157 referred to above, i.e., oxygen and between about 2% to about 12% nitrogen by volume. The gas pressure is preferably at about atmospheric or slightly below.

The photoflash lamp of this invention may be flashed with safety in any position whereas, as noted above, safety precautions dictated that its predecessors be flashed in the base down position only. The improved stability of the combustible supporting structure contributes substantially to the attainment of maximum useful light output because any tendency of the foil structure to collapse effects a marked decrease in useful light out-put.

What I claim is:

1. A photoflash lamp comprising: a sealed light-transmitting envelope; a combustion-supporting gas filling in said envelope; a corrugated strip of flammable foil disposed in said envelope; a supporting framework for said foil secured to an inner wall of said envelope and depending therefrom, said framework including support wires threaded through apertures provided therefor in said foil,

said support. wires being shaped to conform to the contour of said corrugations and being substantially in contact therewith along the major portion of their length; and ignition means disposed in said envelope in operative relationship with respect to said foil;

- 2. A combustible assembly for a photoflashlampcorm prising: a corrugated strip of flammable foil; and support wires threaded through apertures provided therefor in-said foil, said support wires being shaped to conform to the contour of said corrugations-and being substantially incontact therewith along the major portion of their length.

2,057,583 May Oct. 13, 1936 2,289,876 De Margitta July 14, 1942 FOREIGN PATENTS 737,594 Great Britain Sept. 28, 1955 

